Preheat oven to 350°F and line an 8x8* square pan with parchment paper.
In a mixing bowl combine the butter, flour, brown sugar and salt. Press into the bottom of the prepared pan. Bake for 12 minutes.
Core, peel, and thinly slice 4-5 apples (or however many it takes to get 4 cups). Set aside.
In a small bowl, combine the caramel, salt, cinnamon, brown sugar and flour. Pour over the apples and gently stir to coat the apples with the caramel mixture.
Spoon the apples over the crust and use your hands to press them down so they're in a nice even layer. Set aside.
In a medium bowl, use a fork to combine the butter, brown sugar, flour, oatmeal and cinnamon. Sprinkle over the apples and gently press down.
Bake an additional 35-40 minutes, or until the apples are soft.
Let cool; drizzle with additional caramel sauce and spinkle with additional salt, if desired. Serve as is, or with a scoop of ice cream!
Notes
*If you don't have an 8x8 square pan, I recommend using a 9x9 square pan. Because the bars will be slightly thinner, it may take 5 minutes less in the oven.